Arenite, shale, dolostone, siltstone, conglomerate, chert, and limestone; Lower Ordovician marine outer continental-shelf deposits; central Idaho (IDOl;0)

State	Idaho
Name	Arenite, shale, dolostone, siltstone, conglomerate, chert, and limestone; Lower Ordovician marine outer continental-shelf deposits; central Idaho
Geologic age	Early Ordovician
Original map label	Ol
Comments	Unit also included informally named sandy siltstone and quartzite of the Rob Roy mine area, according to Isaacson (1983).
Primary rock type	arenite
Secondary rock type	shale
Other rock types	dolostone (dolomite); siltstone; conglomerate; chert; limestone
Lithologic constituents	Major Sedimentary > Clastic > Sandstone > Arenite (Bed)Clayton Mine Quartzite (feldspathic quartzite) Minor Sedimentary > Clastic > Siltstone (Bed)sandy siltstone of the Rob Roy mine area Sedimentary > Carbonate > Dolostone (Bed)Bayhorse Dolomite, dolomitic limestone, limestone Sedimentary > Clastic > Mudstone > Shale (Bed)Ramshorn Slate and argillite Incidental Sedimentary > Carbonate > Limestone (Bed)limestone, sandy limestone, dolomitic limestone Sedimentary > Chemical > Chert (Lense)chert lenses in Bayhorse Dolomite Sedimentary > Clastic > Conglomerate (Lense)thin lensed of pebbly qtzt cgl in Clayton Mine qtzt
Map references	Bond, J.G., Kauffman, J.D., Miller, D.A., and Venkatakrishnan, Ramesh, 1978, Geologic map of Idaho: Moscow, Idaho, Idaho Bureau of Mines and Geology, with contributions from U.S. Geological Survey, scale 1:500,000.
Unit references	Bond, J.G., Kauffman, J.D., Miller, D.A., and Venkatakrishnan, Ramesh, 1978, Geologic map of Idaho: Moscow, Idaho, Idaho Bureau of Mines and Geology, with contributions from U.S. Geological Survey, scale 1:500,000. Isaacson, P.E., 1983, Stratigraphic correlation of the Paleozoic and Mesozoic rocks of Idaho: Moscow, Idaho, Idaho Bureau of Mines and Geology, Information Circular 37. Ross, C.P., 1934, Correlation and interpretation of Paleozoic stratigraphy in south-central Idaho: Geological Society of America Bulletin, v. 45, no. 5, p. 937-1000. Rember, W.C. and Bennett, E.H., 1979, Geologic map of the Challis quadrangle, Idaho: Moscow, Idaho, Idaho Bureau of Mines and Geology, Geologic Map Series, Challis 2o quadrangle, scale 1:250,000. Hobbs, S.W. and Hays, W.H., 1990, Ordovician and older rocks of the Bayhorse region, Custer County, Idaho: U.S. Geological Survey Bulletin, 1891, 40 p., (incl. geologic map, scale 1:125,000). [http://pubs.er.usgs.gov/publication/b1891]
Geographic coverage	Custer